Currently, only a limited number of serum protein markers exist for a range of tumors, and most have not proved useful for early detection. Membrane-bound folate receptor (FR) alpha is a promising tumor marker for detection of FR alpha-positive tumors. Studies of human tumors show that, FR alpha is over-expressed in epithelial tumors of the ovary, kidney, endometrium, breast and brain compared to normal cells, is identifiable in early disease, increases with tumor progression and stage, and is associated with decreased survival. Importantly, FR alpha is released as a soluble form (sFR alpha) into the circulation and is relatively absent in normal serum, suggesting it may be a promising serum marker for FR alpha-positive tumors. In addition, FR alpha autoantibodies are detected in serum of individuals with folate-related disorders, signifying that the autoantibodies could be another potential biomarker of FR alpha-positive tumors. To our knowledge, no study has investigated their presence in the serum of individuals with FR alpha-positive tumors. We hypothesize that sFR alpha and FR alpha antibodies will be higher among women with ovarian cancer than women without cancer and, specifically, higher among women with early-stage cancer. We focus on ovarian cancer in this application because FR alpha is over-expressed in >90% of non-mucinous epithelial ovarian tumors and is expressed at much lower levels in other tumors; therefore, we anticipate greater likelihood of designing and optimizing assays for FR alpha detection using serum from these patients; and because ovarian cancer is one of the most difficult human diseases to diagnose and treat. Our approach will be to design, develop, and optimize quantitative assays to measure these analytes, and apply each assay to archived, pre-therapeutically collected serum from 30 patients with ovarian cancer (15 early- stage) and 30 women without cancer who participated in a case-control study at Mayo Clinic. Our intent at this initial stage of biomarker discovery is to assess if our assays can detect the analytes truthfully by validating them against FR alpha expression levels in the tumors of the cases and from serum of controls without cancer as reference groups. The data generated from this study, if positive as we expect, will be the basis of a larger analysis that apply these assays to other tumor types with several aims including assessment of diagnostic potential, which is the ultimate goal of biomarker discovery. [unreadable] [unreadable] [unreadable]